Catheters are widely used by the medical profession for a variety of purposes and procedures. For example, catheters are commonly used in the treatment of atherosclerotic lesions or stenoses formed on the interior walls of the arteries. One procedure developed for the treatment of such lesions or stenoses is coronary angioplasty. The most commonly practiced angioplasty procedure is known as percutaneous transluminal coronary angioplasty, or PTCA. According to this procedure, a dilatation catheter having a balloon located at its distal end is guided through the patient's vasculature such that the balloon is positioned within the stenosis. When the catheter is advanced through the patient's vasculature to the treatment site, the balloon is in a deflated state such that the catheter has a minimum cross-section. Once the balloon is positioned across the treatment site, the balloon is inflated one or more times to dilate the stenosis and open the restricted area of the artery. Finally, the balloon is deflated and the catheter is removed from the patient's vasculature.
Typically, the dilatation catheter is maneuvered through the patient's vasculature with the use of a flexible guidewire having a diameter of approximately 0.010 to 0.018 inches and a length of about 180 centimeters. The distal end of the guidewire is extremely flexible so that it may be routed through the convoluted arterial pathway to the site of the stenosis. After the distal portion of the guidewire is positioned across the stenosis, a dilatation catheter having a lumen adapted to receive the guidewire is advanced over the guidewire until the balloon is positioned within the stenosis. Alternatively, the guidewire and catheter may be advanced together within the patient's vasculature to the treatment site with the distal end of the guidewire protruding from the distal end of the catheter.
The prior art includes three types of catheters for use with a guidewire: "over-the-wire" catheters, "rapid exchange" catheters and "fixed-wire" catheters.
A conventional over-the-wire catheter comprises a guidewire lumen, which extends throughout the length of the catheter. In use, the guidewire is disposed entirely within the catheter guidewire lumen except for its proximal and distal ends which protrude from the proximal and distal ends of the catheter, respectively. A typical over-the-wire balloon dilatation catheter is disclosed in Simpson et al. U.S. Pat. No. 4,323,071.
Such over-the-wire catheters have many advantages attributable to the full-length guidewire lumen. For example, these type catheters have good stiffness and pushability for advancing the catheter through the convoluted vasculature to the treatment site. Further, the guidewire lumen provides a continuous conduit between the proximal and distal ends of the catheter for transporting radiocontrast dye to the treatment site or for enabling pressure measurements. In addition, the full-length guidewire lumen allows for the exchange of guidewires within an indwelling catheter, should that be desired.
Despite these advantages, there are many undesirable complications associated with the use of over-the-wire catheters. For example, during a catheterization procedure, it may be necessary to thread a catheter on or off an indwelling catheter, or exchange an indwelling catheter for another catheter over an indwelling guidewire. When advancing or withdrawing a catheter over an indwelling guidewire, the physician must grip the proximal portion of the guidewire extending outside the patient to maintain the position of the distal portion of the guidewire across the treatment site. However, the length of a conventional over-the-wire catheter, typically on the order of 135 centimeters, is greater than the length of the proximal portion of a standard guidewire which protrudes out of the patient. Accordingly, it is necessary to extend the guidewire a sufficient distance outside the patient so that the physician may maintain his or her grip on the proximal portion of the guidewire while threading an over-the-wire catheter on or off an indwelling guidewire. The additional length of guidewire needed is typically provided through the use of a guidewire extension which is temporarily "linked" or attached to the proximal end of the guidewire. Once the catheter has been threaded onto the guidewire extension and advanced over the guidewire through the patient's vasculature, the guidewire extension may be detached from the guidewire.
Alternatively, an exchange wire on the order of 300 centimeters may first be guided through the patient's vasculature such that its distal portion is positioned across the stenosis. The catheter may then be advanced over the exchange wire without disturbing the position of the distal end of the wire. After the balloon located at the distal end of the catheter is positioned within the stenosis, the exchange wire may be removed from the guidewire lumen and replaced with a shorter, easier to handle guidewire.
A number of alternative catheter designs have been developed in an attempt to address these issues. One such design is the fixed-wire catheter, which comprises a catheter having an internally fixed guidewire or stiffening element. Catheters of this design are readily maneuverable and relatively easy to position within the patient's vasculature without the use of a separate guidewire. However, because these catheters do not use a separate guidewire, the administering physician is unable to maintain guidewire access to the treatment site while removing the catheter. Thus, if it were necessary to exchange the catheter, the physician must remove the indwelling catheter and renegotiate the arterial pathway to the treatment site with the replacement catheter.
Another alternate design is the "rapid exchange" type catheter and guidewire system. Generally, a rapid exchange catheter includes a guidewire lumen which extends along only a short shaft section near the distal end of the catheter. Accordingly, when the catheter is advanced over the guidewire, the guidewire is located outside the catheter except for the short segment which passes through the guidewire lumen at the distal end of the catheter. In use, a conventional length guidewire is routed through the patient's vasculature such that its distal end is positioned across the treatment site. The distal end of the catheter is then threaded onto the proximal end of the guidewire. Since the guidewire lumen is relatively short, the catheter may be fully threaded onto the guidewire without linking an extension wire or using a long exchange wire. Similarly, when it is desired to perform a catheter exchange procedure, the catheter may be withdrawn over an indwelling guidewire without the use of a guidewire extension or an exchange wire.
Although such a rapid exchange catheter system may eliminate the need for an extension wire or a long exchange wire, it presents significant disadvantages. For example, because these catheters have a truncated guidewire lumen, they do not provide the same stiffness and pushability as an over-the-wire catheter. Further, it has been found that as these catheters are advanced or withdrawn along the guidewire, the exposed portion of the guidewire may buckle or bow relative to the catheter and possibly inflict damage to the inner walls of the patient's vasculature. Furthermore, there exists a significant risk of guidewire entanglement in procedures involving multiple guidewires. In addition, unlike over-the-wire catheters, it is not possible to exchange guidewires in an indwelling rapid exchange catheter.
Therefore, there exists a need for an improved catheter device and method of use which incorporates the benefits of both the over-the-wire catheters and the rapid exchange catheters, but without their attendant drawbacks.